1. Field of the Invention
For a long time, articulation devices have already been known that are positioned between the seating portion and the back portion of a seat in order to obtain a desired tilting angle of the back portion with respect to the seating portion.
These devices are also utilized to raise seats, i.e. to control both the tilting angle and the height of the seating portion of a seat. The motion is, besides, normally called "control of the seat position".
2. Description of the Prior Art
The mechanisms used, that are either continuous or discontinuous, include fixed parts and movable parts, interlinked by means of different mechanical members which are submitted to numerous stresses mainly in case of accidental shocks resulting in the disassembly by rupture of some members such as toothings, cams rolls, gears, etc. used to link together the fixed portions and the movable portions and to define the relative positioning of the two portions of the seat or of the seat itself, accordingly as the back portion or the position of the seat is to be controlled.
In the event these mechanisms are subjected to stresses exceeding the normal allowable stresses, in a first phase, in the area that contributes to positioning, reversible deformations or settlements in positioning and strains occur but not leading to rupture or breaking-off of mechanisms, and in such circumstances, it is possible to succeed, by various means, in taking up the deformations and strains to avoid mechanisms from breaking-off or being slashed and having deformations or bendings from being formed in this manner.
But, in the presence of far more severe stresses, strains or even ruptures occur leading to an almost complete destruction of these mechanisms. This is considered as being of very great importance since the seats and their components must resist very strong stresses as, very often, in modern vehicles, the safety belts are integral with these seats.
The present invention overcomes these inconveniences and difficulties by providing mechanisms built in order to provide a temporary locking of the movable parts with respect to the fixed parts, in the presence of high stresses, without any permanent strain or rupture so that when these stresses are terminated, the different members of the mechanism involved therewith are practically brought back to their previous position without any hysteresis and are thus ready for a new normal operation.